It’s probably not worth it your time to hack a Verizon MiFi but here’s a great blog post showing you that it can be done and vulnerabilities that exist within the default Verizon WPA settings.
The Verizon MiFi is a great tool, but the engineering team who created the default password mechanism should have taken into consideration the limited entropy in the selection of passwords, and the well-publicized attacks against WPA-PSK networks to limit customer exposure.